hard-headed diabetic mom

My mother has diabetes. This disease runs through her family. She had her medical check-up and had been explained already what are the foods allowed and prohibited to her. She's been taking her maintenance medication regularly. But it seems we are having a hard time making her understand that too much sugar and salt are not allowed for her. She really loves sweet and salty foods. Every time we gonna explain to her the situation, she always has the excuse that she's been taking her meds and she'll gonna drink one pitcher of ampalaya decoction to lower her blood sugar. she's such a stubborn mum and we dont know how to handle her with this stuborness.